Thanks @Mugen87,
So I tried what you recommended and I got the lighting effect I was looking for. However, it seems to me that I only have the color corresponding to the first attribute (RMR) value of the geometry_data. Maybe something is wrong with the definition of norm_z.
I made a JSFiddle for this.
The original color coding is this (no lighting properties)
If you could help me debug this, I would really appreciate it !
Thanks,